Hi Jonathan,
Glad to hear the RAM disk solution helped!
However, I suspect that the remaining 'bottleneck' is that you have three out of four cores sitting mostly idle; as discussed at the beginning of this thread, LDA seems only to use one core.
Faster RAM is now unlikely to help you much (I'd expect a percentage improvement only) although more of it will allow a larger RAM disk and therefore solving larger analyses. A faster (single-thread score) CPU will also help - your E5640 looks pretty slow at 1166 (we're disposing of workstations with faster processors than that here), so replacing with an i7-4790k at over 2500 should double the speed, or even more. The 5820 is a little slower, around 2000, but depending on the price you may decide that's a more sensible route.
As a wildcard, if cost matters and you're sure don't need multi-thread power, consider a fast i3 or even a Pentium - I've recently upgraded my home gaming rig with a Pentium G3258 which was just £50 (CPU and cooler) and scores well over 2000, whilst a 4790k currently goes for over £250... Also note that the "k" is strictly speaking unnecessary unless you plan on overclocking.
Cheers,
another Jonathan